Digital BW, The Print

>
>  > Could a few people comment on why they might use the channel mixer
>  > vs. Image/Greyscale (dump color info) &/or simply desaturate?
>
>
>
>Image/grayscale is based on a blend of roughly 60% RED/ 29% Green/ 11% Blue.

Interesting. I have read that the Blue channel is especially prone to 
noise. But given what Blue or Green filters do to skintones in BW 
film photography, i.e exaggerate skin pigmentation and flaws, I'd 
have to guess those percentages were in part chosen to optimize skin 
tone reproduction. In a landscape image, more equal green/red might 
be better.

Optically, though, RG and B represent different wavelengths, and 
slightly different focus planes unless the optics are fully 
corrected, ala "apo" process and enlarging lenses. As green is mid 
spectrum, choosing it from RGB for grayscale, especially from BW 
negs, would seem to put the least demands on the scanner's lens. 
Comparing RG and B versions of a BW image might also reveal something 
about focus accuracy. Might well be different from scanner to 
scanner, too.



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